1. Field of the Invention
The present invention relates to a phase contrast radiation imaging apparatus and a phase contrast radiation imaging method that utilize a Talbot interferometer, and a radiation image detector which is employed by the phase contrast radiation imaging apparatus.
2. Description of the Related Art
The application of Talbot interferometers, in which the Talbot effect is generated by a diffraction grating and another diffraction grating is used to generate Moire fringes, to the field of X ray imaging is being investigated (refer to U.S. Pat. Nos. 5,812,629 and 7,180,979, for example).
U.S. Pat. No. 7,180,979 discloses an X ray imaging apparatus that utilizes a Talbot interferometer constituted by an X ray source, two diffraction gratings, and an X ray image detector.
Japanese Unexamined Patent Publication No. 2006-259264 discloses production of an amplitude diffraction grating by forming deep grooves in resin using X ray lithography.
Japanese Unexamined Patent Publication No. 2007-203063 discloses an X ray apparatus equipped with detection elements which are constituted by a multiplicity of elongate detection strips. This X ray apparatus enables obtainment of phase images by single measurement using each beam, and the number of measurements necessary to obtain phase images can be reduced.
It is necessary to provide two diffraction gratings of sizes equivalent to that of a subject in the X ray imaging apparatus disclosed in U.S. Pat. No. 7,180,979, which is costly. In addition, of the two diffraction gratings, it is desirable for the one toward the X ray image detector to be an amplitude diffraction grating. In this case, it is necessary to produce a diffraction grating having an extremely high aspect ratio and metallic diffraction members at fine pitches. As an example, the width of the diffraction members of such a diffraction grating is 2 μm to 10 μm, and the thickness thereof is 25 μm to 100 μm. It is necessary to employ a special manufacturing method such as that disclosed in Japanese Unexamined Patent Publication No. 2006-259264 in order to produce such a diffraction grating, and it is difficult to produce diffraction gratings having uniform structures.
In the case that a multiplicity of elongate detection strips are provided as in the X ray apparatus disclosed in Japanese Unexamined Patent Publication No. 2007-203063, it is necessary to form the width of each detection strip to be thinner as the number of phase component images taken simultaneously increases. This is also difficult to realize from a manufacturing standpoint.